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The Influence of Order in the Cation Sublattice of MgAl₂O₄, MgCr₂O₄ and MgFe₂O₄ Spinels on the Kinetics of Topochemical Reactions with Sulphur Oxides

A. Gerle, J. Piotrowski, J. Podwórny

Journal of Ceramic Science and Technology, Vol. 8, No. 2 (2017), pp. 183-192

DOI: 10.4416/JCST2016-00077

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Abstract

Spinel-containing materials are used as refractories for high-temperature unit linings. A crucial element of the conditions in which they are used is gaseous corrosion caused by sulphur oxides. The aim of the study was to investigate the kinetics of topochemical reactions between magnesia spinels and sulphur oxides and influence of inversion in the structure of the spinels on this reaction. Magnesia spinels: MgAl2O4, MgFe2O4, MgCr2O4 were used for the kinetic investigations. It was found that inversion in the case of MgAl2O4 begins at approx. 800 K, for MgFe2O4 at around 700 K while in the case of MgCr2O4 the phenomenon of inversion does not occur. The kinetic measurements were conducted within the temperature range of: 573 – 1073 K for MgAl2O4, 773 – 1073 K for MgCr2O4 and 573 – 1173 K for MgFe2O4. The investigations confirmed that the main product of reaction identified in all the cases was MgSO4. The inversion of the structure of MgFe2O4 and MgAl2O4 magnesia spinels was observed to influence the kinetics of their topochemical reactions with sulphur oxides. It is noteworthy that the obtained results indicate that structure inversion has a greater impact on the change of reactivity of MgFe2O4 than of MgAl2O4 spinel.

Keywords

Order-disorder transformation, spinel, corrosion, refractories, sulphur oxides

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